JP2019170112A - Voltage converter, vehicle using voltage converter and control method of voltage converter - Google Patents

Abstract

An object of the present invention is to suppress an influence on an output of a power supply device when a current taken out of a conversion circuit is limited. A power supply device receives a power generation amount generated by a power supply device, and obtains an upper limit value of a current that can be extracted from a conversion circuit that increases a voltage input from the power supply device, using a relationship that changes with the operation of the conversion circuit. The lower limit voltage of the conversion circuit is determined from the power generation amount and the upper limit current value, and the voltage on the output side of the conversion circuit is controlled to exceed the lower limit voltage. With this configuration, even if the voltage converter limits the current drawn from the conversion circuit, the effect on the output of the power supply device can be suppressed. [Selection] Figure 2

Description

  The present invention relates to a voltage converter and a technique for using the same.

  In a power system circuit, a voltage converter that boosts a voltage may be used. For example, in a fuel cell vehicle, the electric power generated by the fuel cell is boosted by a boost converter provided in the voltage converter and supplied to a load such as a driving motor. This is because increasing the voltage has many advantages such as a reduction in the amount of current required to supply the same power and a reduction in loss. For example, the loss also occurs due to the resistance of wiring such as a bus bar or the ON resistance of a switching element. Since such a loss increases in proportion to the square of the current amount, the loss increases as the circuit using a high current such as a power system. Thus, the voltage converter increases the voltage and reduces the amount of current required for the same power.

  In such a voltage conversion device, circuit components that constitute a circuit due to heat generated by loss, such as wiring of switching elements, resistors, bus bars, relays that turn power on and off, and the like, are prone to failure. For this reason, as seen in Patent Document 1, in the voltage conversion device including the booster circuit, the temperature of the cooling water that cools the voltage conversion device is detected, and when the temperature of the cooling water increases, power is supplied to the voltage conversion device. The fuel cell output is limited.

JP 2011-87406 A

  The technology disclosed in Patent Document 1 is not limited to a configuration using a fuel cell, and in a circuit configuration using a power converter, the maximum current supplied from the power source is a time that does not hinder motor operation based on the cooling water temperature. It is an excellent one limited by the range. Since such a voltage converter originally converts a voltage in order to increase efficiency, there is always a demand for minimizing the loss associated with the conversion.

  The voltage conversion device according to the present disclosure can be realized as the following forms.

[1] The first form is a form as a voltage converter. This voltage conversion device is connected to the power supply device and increases the voltage input from the power supply device. The voltage conversion device includes a conversion circuit that converts a voltage from the power supply device; an input unit that inputs a power generation amount generated by the power supply device; and a control unit that controls the conversion circuit. The control unit obtains an upper limit current value, which is an upper limit value of the current that can be extracted from the conversion circuit, by using a relationship determined from a temperature increase of the conversion circuit accompanying operation of the conversion circuit; A lower limit voltage control unit that obtains a lower limit voltage of the conversion circuit from the power generation amount of the apparatus and the upper limit current value, and controls the output side voltage of the conversion circuit to exceed the lower limit voltage;
According to such a voltage conversion device, an upper limit current value that is an upper limit of the current that can be extracted from the conversion circuit is obtained using a relationship determined from the temperature rise of the conversion circuit accompanying the operation of the conversion circuit, and further, the power generation amount of the power supply device and The lower limit voltage of the conversion circuit is obtained from the upper limit current value, and control is performed so that the voltage on the output side of the conversion circuit exceeds the lower limit voltage. Accordingly, it is possible to suppress the occurrence of a situation in which excessive current is taken out when the temperature of the conversion circuit is high and deterioration of the conversion circuit is accelerated.
[2] In such a voltage converter; the upper limit current calculation unit sets the relationship as the upper limit current value when the conversion circuit is at the first temperature, and the temperature of the conversion circuit is higher than the first temperature. It may be stored as a relationship that is higher than the upper limit current value at the second temperature. By so doing, it is possible to easily realize the relationship of reducing the upper limit current value as the temperature of the conversion circuit is higher.
[3] In such a voltage conversion device; the upper limit current calculation unit associates the temperature increase of the conversion circuit as a temperature time using an elapsed time since the conversion circuit started operation, and the relationship is It may be stored as a relationship in which the upper limit current value gradually decreases with an increase in temperature time. Since the temperature of the conversion circuit tends to increase in proportion to the elapsed time from the start of use, the relationship for reducing the upper limit current value can be easily realized as the temperature of the conversion circuit increases.
[4] In the above-described voltage conversion device; the upper limit current calculation unit may calculate the elapsed time when the loss of the conversion circuit after the conversion circuit starts operation is a first magnitude. May be converted into the temperature time at a larger rate than in the case of the second size smaller than the first size. Since the temperature rise of the conversion circuit is caused by a loss in the conversion circuit, the temperature time can be made to correspond more accurately to the temperature rise of the conversion circuit.
[5] In such a voltage converter, when the conversion circuit that has once stopped operating resumes operation, the upper limit current calculation unit sets the initial value of the upper limit current value according to the state of the conversion circuit at the time of restart. It may be set. In this way, when the conversion circuit resumes operation, the upper limit current value can be set according to the state of the conversion circuit, so that the temperature is sufficiently lowered so that the conversion circuit stops for a short time and starts operation again. Even in such a case, the upper limit current value can be brought close to an appropriate value.
[6] In the above-described voltage conversion device; at least a time detection unit that calculates an elapsed time after the conversion circuit has stopped converting; an outside air temperature detection unit that detects a temperature outside the conversion circuit; The upper limit current calculation unit includes the detected elapsed time after the stop when the conversion circuit restarts the operation after the conversion circuit stops the operation, and the conversion circuit stops the operation. It is good also as what calculates based on the above-mentioned temperature rise and the detected outside air temperature, and calculates the above-mentioned upper limit current value at the time of resumption of the conversion circuit operation. In this way, the upper limit current value when the operation of the conversion circuit is resumed can be brought close to an appropriate value with a simple configuration based on time.
[7] In such a voltage converter, a voltage output from the power supply device and a current value extracted from the power supply device may be input as the power generation amount. In this way, the power generation amount of the power supply device can be easily obtained.
[8] As a second aspect, a vehicle is provided. The vehicle includes a power supply device selected from a battery, a fuel cell, and a generator; the voltage conversion device described above; and a load that operates using a voltage converted by the voltage conversion device. Such a vehicle operates a load by power generation by a power supply device. Such a load may be a drive motor or an auxiliary motor of the vehicle. The upper limit of the current flowing to the load can be appropriately limited.

  In addition to this, the present invention includes various methods such as a method for controlling a voltage converter, a method for manufacturing a voltage converter, a configuration as a moving body using the voltage converter, a method for manufacturing a moving body, and a current limiting method in the voltage converter. It is realizable as an aspect.

The schematic block diagram which illustrates the hardware constitutions in each embodiment. The flowchart which shows the boost converter control processing routine in 1st Embodiment. The graph which shows an example of the relationship between temperature time Ton and upper limit electric current value Aup. The graph which shows the other example of the relationship between temperature time Ton and upper limit electric current value Aup. The flowchart which shows the boost converter control processing routine in 2nd Embodiment. The flowchart which shows the boost converter control processing routine in 3rd Embodiment. Explanatory drawing which shows the mode of the fall of the temperature inside a boost converter by linear approximation. Explanatory drawing which shows the relationship between outside temperature THa and the coefficient K. FIG. Explanatory drawing which illustrates the relationship between time t and ultimate temperature THb after the operation start.

A. Hardware configuration of the embodiment:
The hardware configuration of some embodiments described below will be described. As shown in FIG. 1, a fuel cell vehicle (hereinafter simply referred to as a vehicle) 10 including the voltage conversion device according to the embodiment includes a fuel cell system 20 as a power supply device, and electric power generated by the fuel cell system 20. Is used to drive an electric motor or the like provided in the vehicle 10. As such an electric motor, there are auxiliary machines such as a drive motor 62 for generating a driving force of the vehicle 10 and an air compressor motor (hereinafter referred to as an ACP motor) 24. In the embodiment described below, the drive motor 62 corresponds to a load.

  The fuel cell system 20 has various configurations such as a fuel cell 22, an intake / exhaust system that sends hydrogen or air as an oxidant gas to the fuel cell 22, and a cooling water circulation system that cools the fuel cell 22. Is included. Since such a configuration for operating the fuel cell 22 is well known, most of the illustration in FIG. 1 is omitted, and the ACP motor 24 for feeding air to the fuel cell 22 via the air supply pipe 23 and the intake air temperature THa are read. Only the intake air temperature sensor 25 is shown.

  The fuel cell system 20 is controlled by the fuel cell ECU 26. The fuel cell ECU 26 detects the state of the fuel cell system 20, for example, the intake air temperature sensor 25 described above that detects the intake air temperature THa, the voltage sensor 27 that measures and outputs the output voltage Vfc of the fuel cell 22, and the output current. It is connected to a current sensor 28 that measures and outputs Afc. The fuel cell ECU 26 receives various information from the fuel cell system 20 and outputs a control signal Sfc to the fuel cell system 20 to control the supply amount of fuel gas, the supply amount / pressure of air, and the like.

  The vehicle 10 includes a boost converter 30 as a conversion circuit connected to a power supply line from the fuel cell 22, a step-up / down converter 40 connected to a power supply line on the output side of the boost converter 30, and the like. The boost converter 30 is a converter that boosts the output voltage Vfc of the fuel cell 22 by about twice. The reason why the output voltage of the fuel cell 22 is increased about twice by the boost converter 30 is that the amount of current when driving the drive motor 62 connected to the output side of the boost converter 30 via the inverter 61 is kept low. Because. In general, the loss in the wiring (including the bus bar) is proportional to the square of the current. Therefore, the efficiency of the entire system can be increased by reducing the amount of current. An inverter 51 that drives the ACP motor 24 is also connected to the output side of the boost converter 30. The ACP motor 24 and the drive motor 62 are permanent magnet type three-phase motors in this embodiment, and are driven by the three-phase AC converted by the inverters 51 and 61.

  The operation of boost converter 30 is controlled by boost ECU 36. The step-up ECU 36 reads the generated voltage Vfc, the output current value Afc, and the like from the voltage sensor 27 and the current sensor 28 described above to obtain an upper limit current value Aup described later, or sets the output target voltage Vht to the boost converter 30. Or give instructions. The power generation amount of the fuel cell 22 is obtained by multiplying the power generation voltage Vfc input from the voltage sensor 27 by the output current value Afc input to the current sensor 28. Such information may be read directly from the sensor, or may be collected by the fuel cell ECU 26 and received from the fuel cell ECU 26 using an in-vehicle LAN or the like. In this case, the power generation amount Wfc may be received. The boost converter 30 that boosts the voltage output from the fuel cell 22 described above corresponds to a conversion circuit, and the boost ECU 36 that receives signals from the voltage sensor 27 and the current sensor 28 to control the boost converter 30 has an input unit and a control. It corresponds to the part. The upper limit current calculation unit, the lower limit voltage control unit, the time detection unit, and the like are realized by executing processing to be described later in the boost ECU 36. Therefore, the configuration in which the boost converter 30 and the boost ECU 36 are combined corresponds to a voltage converter.

  The buck-boost converter 40 performs bidirectional voltage conversion and power exchange between the output side of the boost converter 30 and the battery 43. Before the buck-boost converter 40 and the fuel cell 22 start power generation, the power charged in the battery 43 is boosted, and the auxiliary device such as the ACP motor 24 is operated to start the fuel cell system 20. Alternatively, while the fuel cell 22 cannot sufficiently generate power, such as before the warm-up of the fuel cell 22 is completed, the power of the battery 43 is increased and the drive motor 62 is driven via the inverter 61 to drive the vehicle. . On the other hand, when the vehicle 10 performs a braking operation, the buck-boost converter 40 steps down the electric power regenerated by the drive motor 62 and charges the battery 43. The drive motor 62 is controlled by a motor ECU 66, and the motor ECU 66 outputs a control signal Sbt to the step-up / down converter 40 depending on whether the drive motor 62 is in a power running state or a regenerative state, and performs step-up and step-down processing. And its output voltage. In addition, the battery ECU 46 detects the state of charge of the battery 43, for example, the SOC.

B. Control of the first embodiment:
Next, the boost converter control process of the first embodiment will be described. The boost converter control processing routine shown in FIG. 2 is repeatedly executed at predetermined intervals after the fuel cell system 20 is activated and the fuel cell 22 starts generating power at the rated power. This process is a process executed by the boost ECU 36. In addition to this processing, the fuel cell ECU 26 controls the operation of the fuel cell system 20, particularly the fuel cell 22, the motor ECU 66 controls or monitors the step-up / down converter 40, and the battery ECU 46 controls or monitors the state of the battery 43. .

  When the process shown in FIG. 2 is started, the boost ECU 36 first determines whether or not the output current value Afc of the fuel cell 22 read from the current sensor 28 is greater than 0 (step S110). The output current value Afc of the fuel cell 22 being greater than 0 means that the fuel cell 22 is operating and outputting. Therefore, if the fuel cell 22 is in operation, a process for increasing the temperature time Ton (step S200) is performed. If the fuel cell 22 is not operating, a process for resetting the temperature time Ton (step S300) is performed. .

  The temperature time Ton is focused on the fact that the boost converter 30 operates in response to the power generated by the fuel cell 22, the internal temperature of the boost converter 30 increases with the operation, and decreases when the boost converter 30 is not in use. This is a variable that reflects the rise / fall of the temperature of the converter 30 as the elapsed time. When the temperature of boost converter 30 increases, upper limit current value Aup that can be extracted from boost converter 30 is reduced in order to avoid deterioration of boost converter 30. The reason for obtaining the temperature time Ton is to obtain the upper limit current value Aup. In the temperature time increase process (step S200) of the first embodiment, the temperature time Ton is simply increased gradually as the actual time from the start of use of the boost converter 30, and in the temperature time Ton reset process (step S300), the boost converter It is reset to the value 0 when 30 is stopped.

After calculating the temperature time Ton, a process of selecting the upper limit current value Aup is performed (step S400). An example of the relationship for obtaining the upper limit current value Aup from the temperature time Ton is shown in FIG. In this example, the upper limit current value Aup is the value Amx until the temperature time Ton is up to the time t1, the value Am1 between the time t1 and the time t2, and the value Am1 after the temperature time Ton. That is, the relationship shown in FIG. 3 indicates that the upper limit current value Aup when the boost converter 30 is at the first temperature is the upper limit current when the temperature of the boost converter 30 is the second temperature higher than the first temperature. The boost ECU 36 stores this relationship in a built-in memory. In the first embodiment, since the temperature time Ton coincides with the real time, the upper limit current value Aup is switched to three stages and decreases with time. The relationship between the temperature time Ton and the upper limit current value Aup is not limited to that shown in FIG. 3, and may be switched more finely in multiple stages. For example, as shown in FIG. Also good. Such a relationship may be, for example, a relationship shown as the following formula (1).
Upper limit current value Aup = Ami + (Amx−Ami) / (Ton + 1) (1)
Here, the value Amx is the maximum value of the upper limit current value Aup, and the value Ami is the minimum value of the upper limit current value Aup. The minimum value Ami of the upper limit current value Aup is defined as the upper limit current value when the temperature time Ton is equal to or longer than a predetermined time and the internal temperature is constant due to the balance between heat generation and heat dissipation of the boost converter 30.

After selecting the upper limit current value Aup in this way, processing for obtaining the lower limit voltage Vlw is performed (step S500). The lower limit voltage Vlw is a voltage that can extract the maximum current (that is, the upper limit current value Aup) from the power input to the boost converter 30, that is, the generated power of the fuel cell 22. Expressed as equation (2), the lower limit voltage Vlw is
Vlw = λ × Vfc × Afc / Aup (2)
Can be obtained as The coefficient λ is the conversion efficiency of the boost converter 30. If the conversion efficiency is negligible, the calculation may be performed with λ = 1.

  After obtaining the lower limit voltage Vlw in this way, it is next determined whether or not the target voltage Vht instructed to the boost converter 30 is greater than the lower limit voltage Vlw (step S120). If the target voltage Vht output from the boost converter 30 is greater than the lower limit voltage Vlw, the target voltage Vht is output as it is as a voltage command value for the boost converter 30 (step S130). The lower limit voltage Vlw is output as a voltage command value for the converter 30 (step S140). As a result, the output voltage of boost converter 30 is controlled to be equal to or higher than lower limit voltage Vlw, and as a result, the current drawn from boost converter 30 does not exceed upper limit current value Aup. After the output of the voltage command value (step S130 or S140), the process exits to “NEXT” and ends the present processing routine.

  According to the first embodiment described above, the temperature inside the boost converter 30 from the start of use of the boost converter 30 is estimated as the temperature time Ton reflecting the elapsed time from the start of use, and this temperature time Ton and the upper limit current By referring to a predetermined relationship with the value Aup, an upper limit current value Aup that is the upper limit of the current extracted from the boost converter 30 is obtained, and the output voltage of the boost converter 30 is set to the lower limit voltage Vlw so as not to exceed this current. That's it. Therefore, it is possible to suppress the occurrence of a situation in which excessive current is taken out when the temperature inside boost converter 30 is high and deterioration of boost converter 30 is accelerated. In addition, since it is not necessary to measure the temperature inside the boost converter 30, this can be realized with a simple configuration. Furthermore, according to the first embodiment, the generated power required for the fuel cell 22 does not fluctuate due to changing the upper limit current value Aup.

C. Control of the second embodiment:
Next, a second embodiment will be described. The vehicle 10 of the second embodiment has the same hardware configuration as that of the first embodiment in that a boost converter 30 corresponding to a voltage converter and a fuel cell 22 corresponding to a power supply device are provided. In the second embodiment, the processing performed by the boost ECU 36 is different from that of the first embodiment. FIG. 5 is a flowchart showing a main part of a boost converter control processing routine executed by the boost ECU 36 in the second embodiment. FIG. 5 shows from the start of the processing routine of the first embodiment shown in FIG. 2 to step S400. In the second embodiment, the temperature time Ton increase process (step S200) and the temperature time reset process (step S300) are different from the first embodiment.

  Also in the second embodiment, the temperature time Ton increase process (step S200) is executed when power generation by the fuel cell 22 is performed (Afc> 0). The temperature time reset process (step S300) is executed when the power generation of the fuel cell 22 is not performed. In the temperature time reset process (step S300), the variables To1 and To2 used in step S200 are all reset to 0 with the temperature time Ton (step S310).

On the other hand, when the temperature time Ton increasing process (step S200) is executed when the fuel cell 22 is generating power, first, the temperature time Ton is expressed as the following equation (3) with respect to the actual elapsed time T. Is obtained (step S210).
Ton ← Ton_old + (Afc / Amx) ² · T (3)
Here, the suffix “_old” indicates a value when this processing is performed last time, that is, a previous value. Therefore, Ton_old is the previous value of the temperature time Ton obtained when this process was performed last time. Afc is the generated current value of the fuel cell 22, and Amx is the maximum value of the upper limit current value Aup illustrated in FIGS. Since the loss of boost converter 30 is proportional to the square of the current value, the heat generation is small if the current actually flowing into boost converter 30 is small, and the heat generation is large if the current is large. For this reason, how much the actual elapsed time T is reflected in the increase in the temperature time Ton is reflected by the coefficient (Afc / Amx) ² . In this example, as the current Afc flowing into the boost converter 30 is closer to the maximum value Amx of the upper limit current value Aup, the elapsed time is reflected in the temperature time Ton at a larger rate. The temperature time Ton obtained by the equation (3) is used as the previous value Ton_old when this step S200 is executed next time.

  Next, it is determined whether or not the temperature time Ton thus determined exceeds a predetermined threshold time Tj1 (step S212). This time is a time corresponding to the time t1 in FIG. 3 in the case of the first embodiment. If not exceeded (step S212: “NO”), the calculation variables To1 and To2 are set to the temperature time Ton obtained by the above equation (3) (step S218), and step S200 is temporarily terminated, and step S400 is completed. That is, the process proceeds to the selection process of the upper limit current value Aup. At this time, the temperature time Ton is a value obtained by Equation (3), and the upper limit current value Aup is obtained based on the relationship illustrated in FIG. In this case, the current value Aup becomes the maximum value Amx.

When such a process is repeated several times and the temperature time Ton obtained in step S210 exceeds the threshold time Tj1 (step S212: “YES”), in the subsequent step S214, the temperature time Ton is obtained by the following equation (4). .
Ton ← To1_old + (Afc / Am1) ² · T (4)
After obtaining the temperature time Ton according to the equation (4), the latest value of the obtained temperature time Ton is set in the variable To1 (To1 ← Ton). As a result, To1_old is the previous value of the variable To1 set in step S218 when step S214 is executed for the first time, and thereafter becomes the same as the previous value of the temperature time Ton. Am1 is a value determined as a value lower than the maximum value Amx of the upper limit current value Aup illustrated in FIGS. Also in this case, as the current Afc flowing into the boost converter 30 is closer to the value Am1 determined as one of the upper limit current values Aup, the elapsed time is reflected in the temperature time Ton at a larger rate.

  After obtaining the temperature time Ton in this way, it is determined whether or not the temperature time Ton has exceeded a predetermined threshold time Tj2 (step S220). This time is a time corresponding to the time t2 in FIG. 3 in the case of the first embodiment. If not exceeded (step S220: “NO”), the variable To2 for calculation is set to the temperature time Ton obtained by the above equation (4) (step S228), and step S200 is temporarily terminated, and step S400, that is, The process proceeds to the selection process of the upper limit current value Aup. At this time, the temperature time Ton is a value obtained by the equation (4), and the upper limit current value Aup is obtained based on, for example, the relationship illustrated in FIG. In this case, the current value Aup becomes a value Am1 smaller than the maximum value Amx.

If such a process is repeated several times and the temperature time Ton increases, the determinations in steps S212 and S220 are both “YES”. In this case, in step S224, the temperature time Ton is obtained by the following equation (5).
Ton ← To2_old + (Afc / Am2) ²・ T (5)
After obtaining the temperature time Ton according to the equation (5), the latest value of the obtained temperature time Ton is set in the variable To2 (To2 ← Ton). As a result, To2_old is the previous value of the variable To2 set in step S228 when step S224 is executed for the first time, and thereafter becomes the same as the previous value of the temperature time Ton. Am2 is a value determined as the lowest value among the upper limit current values Aup illustrated in FIGS. Also in this case, as the current Afc flowing into the boost converter 30 is closer to the value Am2 determined as one of the upper limit current values Aup, the elapsed time is reflected in the temperature time Ton at a larger rate. That is, when the loss of the boost converter 30 after the boost converter 30 starts operation by the processing of steps S214 and S218 is the first magnitude, the loss of the boost converter 30 is the second smaller than the first magnitude. A process of converting the temperature time Ton at a larger rate than the case of the size of is realized.

  After obtaining the temperature time Ton in this way, step S200 is once ended, and the process proceeds to step S400, that is, the process of selecting the upper limit current value Aup. At this time, the temperature time Ton is a value obtained by the equation (5), and the upper limit current value Aup is obtained based on, for example, the relationship illustrated in FIG. In this case, the current value Aup becomes a small value Am2.

  According to the boost converter 30 of the second embodiment described above, the temperature time Ton is obtained using a ratio determined by the magnitude of the current flowing into the boost converter 30, so that the temperature rise due to the operation of the boost converter 30 is more accurately detected. Thus, the upper limit current value Aup can be obtained, so that the lower limit voltage Vlw can be set to a more appropriate value. Therefore, in addition to the operational effects of the first embodiment, there is an excellent effect that excessive current limitation is not performed.

D. Third embodiment:
Next, a third embodiment will be described. The vehicle 10 of the third embodiment has the same configuration as that of the first and second embodiments, but differs in hardware configuration from the first and second embodiments in the following points. In the third embodiment, the fuel cell ECU 26 outputs the intake air temperature (outside air temperature) THa detected by the intake air temperature sensor 25 shown in FIG. The boost ECU 36 uses the intake air temperature THa received from the fuel cell ECU 26 as the outside air temperature THa. Instead of the intake air temperature sensor 25, an independent outside air temperature sensor may be provided, and the boost ECU 36 may directly read the signal and measure the outside air temperature THa.

  In consideration of the difference in the hardware configuration described above, in the vehicle 10 of the third embodiment, the booster ECU 36 receives the outside air temperature THa via the fuel cell ECU 26, and then the boost converter control processing routine shown in FIG. Execute.

  The step-up ECU 36 in the third embodiment executes the step-up converter control processing routine shown in FIG. The flowchart shown in FIG. 6 is the main part of the boost converter control processing routine (FIG. 2) shown in the first embodiment. FIG. 6 shows from the start of the processing routine of the first embodiment shown in FIG. 2 to step S400. In the third embodiment, the temperature time Ton increase process (step S200) and the temperature time reset process (step S300) are different from the first and second embodiments.

  Also in the third embodiment, the temperature time Ton increase process (step S200) is executed when power generation by the fuel cell 22 is performed (Afc> 0). The temperature time reset process (step S300) is executed when the power generation of the fuel cell 22 is not performed.

In the temperature time Ton increasing process (step S200) performed when the fuel cell 22 is generating electric power, a process for obtaining the temperature time Ton is performed as the following equation (6) with respect to the actual elapsed time T (step S200). S250).
Ton ← Ton_old + A (6)
Here, A is a value that reflects how much the boost converter 30 has risen during the interval of executing this boost converter control processing routine. This value A may be a coefficient for simply gradually increasing the temperature time Ton as in the first embodiment. For example, the amount of power (Vfc × Afc or the like) at which the boost converter 30 is converting the voltage. Alternatively, it may be determined based on a loss occurring in boost converter 30 or may be determined based on outside temperature THa received by boost ECU 36 from fuel cell ECU 26. The determination may be made based on both of them or with reference to other parameters.

On the other hand, when the fuel cell system 20 is not generating power (step S110: “NO”), the following processing is performed as the temperature time Ton reset processing (step S300). First, a process for obtaining a temperature reset time Tof corresponding to the elapsed time after the stop is performed according to the following equation (7) (step S350).
Tof ← Tof_old + B (7)
Here, the temperature reset time Tof is a variable that estimates how the temperature of the boost converter 30 decreases after the use of the boost converter 30 is stopped. The temperature reset time Tof is determined in Steps S352 and S354 following Step S350, because the determination whether or not the fuel cell 22 is generating power and the process of returning the temperature reset time Tof to the value 0 are performed again. While the battery 22 is not generating power, the boost converter control processing routine is incremented by a value B each time the boost converter control processing routine is executed at a predetermined interval, and the fuel cell 22 is in a power generation stopped state (step S110: “NO”). It can be seen that the value is reset to 0 at the timing when power generation is started (step S352: “YES”). After performing the above processing (steps S350 to 354), the temperature time Ton is calculated by the following equation (8).
Ton ← Ton_old-K ・ Tof (8)
However, a guard is applied so that Ton does not become 0 or less. Similarly, the temperature time Ton in the process of step S252 is guarded at a predetermined upper limit value assuming a temperature that may be reached during rated operation. This process is also omitted from the illustration.

Thereafter, when step S200 is completed, the process proceeds to step S400, and processing for obtaining the upper limit current value Aup is performed. When such processing is performed, the temperature time Ton changes as follows.
[1] When the operation of the fuel cell 22 is started, the boost converter 30 starts a boost operation, and the internal temperature rises according to the amount of electric power whose voltage is being converted (here, boosted). Correspondingly, the temperature time Ton increases with time. Then, as shown in FIG. 3 and FIG. 4, the upper limit current value Aup gradually decreases as the temperature time Ton increases, and eventually converges to a constant value.
[2] When the operation of the fuel cell 22 is stopped, the internal temperature of the boost converter 30 gradually cools, and accordingly, the temperature reset time Tof increases. Therefore, while the fuel cell 22 is stopped, the temperature time Ton gradually decreases at a rate obtained by multiplying the temperature reset time Ton by the predetermined coefficient K according to the above equation (8).
[3] Therefore, when the use of the fuel cell 22 is resumed next, the temperature time Ton does not necessarily have the value 0, and reflects the temperature if the inside of the boost converter 30 is not cooled. The upper limit current value Aup immediately after the use of the boost converter 30 is resumed reflects the internal temperature of the boost converter 30.

  As a result, even when the fuel cell 22 is stopped and used again after a short period of time, the upper limit current value Aup can be made to reflect the internal temperature of the boost converter 30, resulting in a lower limit of the boost converter 30. Since voltage Vlw can be set to a value commensurate with this, boost converter 30 is not operated with an excessive amount of power. Therefore, the reliability of the boost converter 30 can be further ensured.

  In this case, the coefficient K may be a predetermined value, but may be obtained as follows. The internal temperature of boost converter 30 decreases with time from the reached temperature THb when the voltage conversion operation is stopped. FIG. 7 shows the state of this reduction approximated by a straight line. The three straight lines shown in FIG. 7 indicate cases where the outside air temperatures THa are THa1, THa2, and THa3, respectively. At this time, the outside air temperature has a relationship of THa1 <THa2 <THa3. That is, the internal temperature of boost converter 30 decreases faster as external temperature THa is lower. Therefore, the value of the coefficient K may be determined according to this inclination. This relationship is illustrated in FIG. The coefficient K is set to be smaller as the outside air temperature THa is higher. Note that the temperature of the boost converter 30 can be determined in a fixed system using a physical model if the overall specific heat, mass, surface area, heat radiation, outside air temperature, current temperature of the boost converter 30 and the like are known. It is possible to calculate. Therefore, such a heat dissipation model may be constructed and calculated in real time, or may be obtained by an approximate expression according to the heat dissipation model. Alternatively, a map may be prepared according to a heat dissipation model and obtained based on this map.

  The internal temperature of boost converter 30 may reach a higher temperature if outside temperature THa is high when boost converter 30 is operating. Therefore, as shown in FIG. 9, the temperature THb of the boost converter 30 during operation of the fuel cell 22 is assumed to increase with the time t, with the outside temperature THa as an initial value, and the temperature time Ton in step S252 is increased. The ratio A to be determined may be determined.

E. Other embodiments:
In each of the above embodiments, the internal temperature of the boost converter 30 is estimated and the upper limit current value Aup is obtained. However, the internal temperature of the boost converter 30 is directly measured by providing a temperature sensor, and the temperature is measured using the value. The upper limit current value A may be set by obtaining the time Ton.

  In the embodiment, whether or not the boost converter 30 is operating is determined based on the power generation current Afc of the fuel cell 22, but may be determined based on an operating current in the boost converter 30 or the like. The boost converter 30 or the like may have a boosting coil. In such a case, the operating state may be determined by a magnetic field generated in the coil.

  The upper limit current value Aup may be obtained by storing the relationship between the upper limit current value and the temperature time Ton in advance as a map as shown in FIG. 3, and may be obtained with reference to this or based on equation (1) or the like. May be. Alternatively, the upper limit current value Aup may be obtained directly from the temperature inside the boost converter.

  In the second and third embodiments, when the internal temperature of the boost converter 30 is likely to rise, the temperature time Ton is reflected in the temperature time Ton. That is, it can be considered that the relationship of FIGS. 3 and 4 is fixed and the temperature time Ton on the horizontal axis is expanded and contracted. Thus, instead of reflecting the internal temperature of boost converter 30 in time, the relationship of FIGS. 3 and 4 may be reflected. The relationship shown in FIGS. 3 and 4 may be prepared for each internal temperature of the boost converter 30, and this may be switched depending on the internal temperature of the boost converter 30.

  In the above embodiment, the boost converter 30 as the conversion circuit performs only boosting, but it may be a step-down converter or a buck-boost converter. Moreover, although the fuel cell was illustrated as a power supply device, a power supply device does not need to be restricted to a fuel cell. The power supply device may be a battery or a generator driven by an internal combustion engine, wind power, wave power, or the like. An apparatus using such a voltage converter may be an electric vehicle, a fuel cell vehicle, a so-called series hybrid vehicle, or a variety of moving bodies such as a motorcycle, a ship, and a train. Of course, you may use for the electric power supply apparatus etc. which used the fuel cell of stationary installation.

  In the above embodiment, the load is a motor for driving the vehicle, but the load may be another motor. Although one drive motor is provided for the entire vehicle, a configuration in which a drive motor is provided for each of the front wheels and the rear wheels, or a configuration as a wheel motor is also applicable. Furthermore, the load may be of other forms such as a heater.

  The present disclosure is not limited to the above-described embodiment, and can be realized with various configurations without departing from the spirit of the present disclosure. For example, the technical features of the embodiments corresponding to the technical features in each embodiment described in the summary section of the invention are intended to solve part or all of the above-described problems, or part of the above-described effects. Or, in order to achieve the whole, it is possible to replace or combine as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate. For example, a part of the configuration realized by hardware in the above embodiment can be realized by software. Further, at least a part of the configuration realized by software can be realized by a discrete circuit configuration.

DESCRIPTION OF SYMBOLS 10 ... Vehicle 20 ... Fuel cell system 22 ... Fuel cell 23 ... Air supply pipe 24 ... ACP motor 25 ... Intake air temperature sensor 26 ... Fuel cell ECU
27 ... Voltage sensor 28 ... Current sensor 30 ... Boost converter 36 ... Boost ECU
40 ... Buck-boost converter 43 ... Battery 46 ... Battery ECU
51 ... Inverter 61 ... Inverter 62 ... Drive motor 66 ... Motor ECU

Claims (9)

A voltage converter connected to a power supply device to increase a voltage input from the power supply device,
A conversion circuit for converting a voltage from the power supply device;
An input unit for inputting a power generation amount generated by the power supply device;
A control unit for controlling the conversion circuit;
With
The controller is
An upper limit current calculation unit for obtaining an upper limit current value that is an upper limit value of the current that can be extracted from the conversion circuit, using a relationship determined from a temperature increase of the conversion circuit accompanying operation of the conversion circuit;
A lower limit voltage control unit that obtains a lower limit voltage of the conversion circuit from the power generation amount and the upper limit current value of the power supply device, and controls the output side voltage of the conversion circuit to exceed the lower limit voltage. Conversion device. The voltage conversion device according to claim 1,
The upper limit current calculation unit sets the relationship between the upper limit current value when the conversion circuit is at the first temperature and the upper limit when the temperature of the conversion circuit is higher than the first temperature. A voltage converter that memorizes a relationship that is higher than the current value. The voltage conversion device according to claim 1,
The upper limit current calculation unit associates the temperature increase of the conversion circuit as a temperature time using an elapsed time since the conversion circuit started operation, and the relationship is increased with respect to the increase of the temperature time. A voltage conversion device that stores the current value as a gradually decreasing relationship. The voltage converter according to claim 3,
The upper limit current calculation unit calculates the elapsed time when the loss of the conversion circuit after the conversion circuit starts operation is a first magnitude, and the loss is smaller than the first magnitude. A voltage conversion device that converts the temperature time into a larger rate than the case of the size of. The voltage converter according to any one of claims 1 to 4,
The upper limit current calculation unit sets an initial value of the upper limit current value according to a state of the conversion circuit at the time of restart when the conversion circuit that has once stopped operation restarts operation. The voltage conversion device according to claim 1,
At least a time detection unit for obtaining an elapsed time after the stop after the conversion circuit stops the conversion;
An outside air temperature detection unit for detecting the temperature outside the conversion circuit;
With
The upper limit current calculation unit is configured to detect the temperature of the conversion circuit when the conversion circuit resumes operation after the operation is stopped, the detected elapsed time after the stop, and the conversion circuit until the conversion circuit stops the operation. A voltage converter that calculates the upper limit current value when restarting operation of the conversion circuit, obtained based on a temperature rise and the detected outside air temperature.   The voltage conversion device according to any one of claims 1 to 6, wherein the input unit inputs a voltage output from the power supply device and a current value extracted from the power supply device as the power generation amount. A power supply selected from a battery, a fuel cell, and a generator; and
The voltage converter according to any one of claims 1 to 7,
A load that operates using the voltage converted by the voltage converter;
Vehicle equipped with. A method for controlling a voltage conversion device including a conversion circuit for increasing a voltage input from a power supply device,
Enter the amount of power generated by the power supply,
The upper limit current value that is the upper limit value of the current that can be extracted from the conversion circuit is determined using a relationship that changes with the operation of the conversion circuit,
A control method for a voltage converter, wherein a lower limit voltage of the conversion circuit is obtained from the power generation amount and the upper limit current value of the power supply device, and the output side voltage of the conversion circuit is controlled to exceed the lower limit voltage.

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